Faculty Profiles - SETTAI Rikio

Papers - SETTAI Rikio

Division display 101 - 120 of about 428 ／ All the affair displays >>

Possibility of Valence-Fluctuatsion-Mediated Superconductivity in Cd-Doped CeIrIn5 Probed by In NQR Reviewed

M. Yashima, N. Tagami, S. Taniguchi, T. Unemori, K. Uematsu, H. Mukuda, Y. Kitaoka, Y. Ota, F. Honda, R. Settai, Y. Onuki

PHYSICAL REVIEW LETTERS 109 ( 11 ) 2012.9

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER PHYSICAL SOC

We report on a pressure-induced evolution of exotic superconductivity and spin correlations in CeIr(In1-xCdx)(5) by means of in-nuclear-quadrupole-resonance (NQR) studies. Measurements of an NQR spectrum and nuclear-spin-lattice-relaxation rate 1/T-1 have revealed that antiferromagnetism induced by Cd doping emerges locally around Cd dopants, but superconductivity is suddenly induced at T-c = 0.7 and 0.9 K at 2.34 and 2.75 GPa, respectively. The unique superconducting characteristics with a large fraction of the residual density of state at the Fermi level which increases with T-c differ from those for anisotropic superconductivity mediated by antiferromagnetic correlations. By incorporating the pressure dependence of the NQR frequency pointing to the valence change of Ce, we suggest that unconventional superconductivity in the CeIr(In1-xCdx)(5) system may be mediated by valence fluctuations.

DOI： 10.1103/PhysRevLett.109.117001

Spin Susceptibility of CeOs4Sb12 Probed by 121Sb-NMR

Mitsuharu Yashima, Hidekazu Mukuda, Yoshio Kitaoka, Hiroaki Shishido, Rikio Settai, Yoshichika ŌnukiMamoru Yogi, Haruo Niki, Hidekazu Mukuda, Yoshio Kitaoka, Hitoshi Sugawara, Hideyuki Sato

J. Phys. Soc. Jpn. 81 Supplement B, SB049/1-4 (2012) 2012.8

de Haas-van Alphen effect and Fermi surface properties in rare earth and actinide compounds (Review Article) Reviewed

Yoshichika Onuki, Rikio Settai

LOW TEMPERATURE PHYSICS 38 ( 2 ) 89 - 153 2012.2

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

Fermi surface properties in rare earth (R) and actinide (An) compounds of RX3 (X: Al, Ga, In, Si, Ge, Sn, Pb), AnX(3), RTIn5 (T: transition metal), and AnTGa(5) are clarified as a function of the number of valence electrons. The electronic state can be changed by applying pressure and magnetic field. A change of Fermi surface properties associated with the metamagnetic behavior and the quantum critical point is also clarified precisely, together with the split Fermi surfaces in the non-centrosymmetric crystal structure, and the de Haas-van Alphen oscillations in the superconducting mixed state. In the quantum critical point region, the conduction electrons, or quasi-particles, are of an f-electron character, with heavy effective masses of 10-100 m(0) (m(0) is the rest mass of an electron) and condense into the unconventional (anisotropic) superconducting state. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3683408]

DOI： 10.1063/1.3683408

Electrical and Magnetic Properties of Quasicrystal Approximants RCd6 (R: Rare Earth) Reviewed

Akinobu Mori, Hisashi Ota, Shingo Yoshiuchi, Ken Iwakawa, Yuki Taga, Yusuke Hirose, Tetsuya Takeuchi, Etsuji Yamamoto, Yoshinori Haga, Fuminori Honda, Rikio Settai, Yoshichika Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 81 ( 2 ) 2012.2

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We measured the electrical resistivity, magnetic susceptibility, magnetization, and specific heat of the quasicrystal approximants RCd6 (R: rare earth, Y-Lu) with a body-centered cubic (bcc) crystal structure. Single crystals were grown by the Cd-self flux method and annealing method. We confirmed that the structural order-disorder transition is realized at about 160K when the lattice constant a is larger than 15.481 angstrom in YCd6, namely, for R = Pr, Nd, Sm, Gd, Tb, Dy, and Yb. At lower temperatures, RCd6 compounds, except non-4f reference compounds YCd6 and LuCd6, and a divalent compound YbCd6, are found to order antiferromagnetically. We clarified that the structural order-disorder transition has a great influence on the magnetic ordering and transport properties. The Neel temperature of RCd6 (R: Nd, Sm, Tb, and Dy) with the structural order-disorder transition is appreciably higher than the de Gennes scaling normalized by the Neel temperature of GdCd6, while the the Neel temperature of RCd6 (R: Ho, Er, and Tm) without the structural transition approximately follows the de Gennes scaling. Moreover, the electrical resistivity of RCd6 with the structural transition decreases monotonically below the Neel temperature, while it increases below the Neel temperature and a large residual resistivity remains at low temperatures in RCd6 without the structural transition. The contribution of an Einstein oscillator to the phonon specific heat is also discussed in YCd6 and LuCd6.

DOI： 10.1143/JPSJ.81.024720

Metamagnetic Behavior in Heavy Fermion Compounds UCo2Zn20 and UIr2Zn20 Reviewed

Y. Hirose, K. Enoki, S. Yoshiuchi, T. Takeuchi, F. Honda, K. Sugiyama, E. Yamamoto, Y. Haga, M. Hagiwara, K. Kindo, R. Settai, Y. Onuki

INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES 2011) 391 2012

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IOP PUBLISHING LTD

The metamagnetic behavior, which is typical in heavy fermion compounds, is observed in UCo2Zn20 and UIr2Zn20 at H-m = 80 and 20 kOe, respectively. Reflecting the metamagnetic behavior, the magnetoresistance is suppressed in magnetic fields larger than H-m, and the corresponding A-value of a Fermi liquid relation in the electrical resistivity sigma = sigma(0) + AT(2) indicates a peak at around H-m. Pressure suppresses this behavior in UIr2Zn20.

DOI： 10.1088/1742-6596/391/1/012021

Field-Induced Ordering in the Heavy Fermion Compound YbCo2Zn20 Reviewed

Yasuyuki Shimura, Toshiro Sakakibara, Shingo Yoshiuchi, Fuminori Honda, Rikio Settai, Yoshichika Onuki

INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES 2011) 391 2012

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IOP PUBLISHING LTD

DC Magnetization of the heavy-fermion compound YbCo2Zn20 was examined at very-low temperatures down to 0.07 K in the field up to 14.5 T. In addition to the nearly-isotropic metamagnetic behavior at 0.6 T, a new metamagnetic behavior is observed in the field variation of magnetization M(H) at 6 T only for H parallel to [111]. For the same field direction, a clear kink appears in the temperature dependence of the magnetization M(T) for fields above 6 T. These results strongly suggest the existence of a new ordered phase induced by magnetic fields. The H - T phase diagram as well as the anisotropy in M(H) above similar to 2 T are best explained by a level crossing of the low-lying crystalline-electric-field states by magnetic fields.

DOI： 10.1088/1742-6596/391/1/012066

Characteristic magnetic phase diagram in heavy-fermion compound YbCo2Zn20 Reviewed

T. Takeuchi, S. Yoshiuchi, M. Ohya, M. Matsushita, S. Yasui, Y. Hirose, K. Sugiyama, F. Honda, R. Settai, Y. Onuki

INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES 2011) 391 2012

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IOP PUBLISHING LTD

We studied the magnetic field versus temperature phase diagram of the heavy-fermion compound YbCo2Zn20 with the cubic CeCr2Al20-type structure by measuring the specific heat, ac-susceptibility, and electrical resistivity under magnetic fields. In a low magnetic field region, a metamagnetic behavior was observed at H-m = 6 kOe for three principal field directions below T-chi max = 0.32 K, at which the temperature dependence of ac-susceptibility shows a local broad maximum. Two crossover lines were found below and above H-m. At high magnetic fields, the heavy-fermion state was rapidly suppressed with increasing magnetic field, and the field-induced ordered phase appeared in a very limited field direction around H parallel to < 111 > above the transition field H-Q = 60 kOe in the temperature range below T-Q = 0.6 K.

DOI： 10.1088/1742-6596/391/1/012072

Effect of magnetic field in heavy-fermion compound YbCo2Zn20 Reviewed

Koji Kaneko, Shingo Yoshiuchi, Tetsuya Takeuchi, Fuminori Honda, Rikio Settai, Yoshichika Onuki

INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES 2011) 391 2012

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IOP PUBLISHING LTD

Inelastic neutron scattering experiments on poly crystalline sample of heavy-fermion compound YbCo2Zn20 were carried out in order to obtain microscopic insights on the ground state and its magnetic field response. At zero field at 300 mK, inelastic response consists of two features: quasielastic scattering and a sharp peak at 0.6 meV. With increasing temperature,a broad peak comes up around 2.1 meV, whereas quasielastic response gets broader and the peak at 0.6 meV becomes unclear. By applying magnetic field, the quasielastic response exhibits significant broadening above 1 T, and the peak at 0.6 meV is obscure under fields. The peaks in inelastic spectra and its temperature variation can be ascribed to the suggested crystal-field model of Gamma(6) - Gamma(8) - Gamma(7) with the overall splitting of less than 3 meV. The observed quasielastic response and its rapid broadening with magnetic field indicates that the heavy-electron state arises from the ground state doublets, and are strongly suppressed by external field in YbCo2Zn20,

DOI： 10.1088/1742-6596/391/1/012026

Specific Heat Study of the Non-centrosymmetric Superconductor LaPt3Si in Magnetic Fields Reviewed

G. Motoyama, M. Shiotsuki, Y. Oda, A. Yamaguchi, A. Sumiyama, T. Takeuchi, R. Settai, Y. Onuki

26TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT26), PTS 1-5 400 2012

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IOP PUBLISHING LTD

We have measured the specific heat of poly- and single-crystalline LaPt3Si samples in various magnetic fields. In zero magnetic field, we observed distinct superconducting transitions at T-c similar to 0.64 K and 0.61 K for the poly- and single crystals, respectively. Temperature T dependences of the specific heat C of both samples around T-c resembled each other and could be well described by an exponential equation for a conventional superconductor at low temperatures. In a magnetic field, a characteristic peak of C/T appeared while the T-c was considerably suppressed. These trends were pronounced for the single crystal. The transition of the polycrystal became broad above 40 Oe and a characteristic tail appeared at temperatures above the peak of C/T. We suggest that the tail is induced by domains that have crystallographic disorders of the non-centrosymmetry and a higher critical magnetic field than that of the bulk. These domains became superconducting at temperatures above the peak of C/T, and then formed the tail. Both the poly- and single-crystalline LaPt3Si samples have been found to show characteristics that are in-between those of type-I and type-II superconductors.

DOI： 10.1088/1742-6596/400/2/022079

Pressure-induced novel superconductivity and heavy fermion state in rare earth compounds Reviewed

Fuminori Honda, Yusuke Hirose, Shingo Yoshiuchi, Shinichi Yasui, Tetsuya Takeuchi, Ismardo Bonalde, Katsuya Shimizu, Rikio Settai, Yoshichika Onuki

26TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT26), PTS 1-5 400 2012

Language：English Publishing type：Research paper (international conference proceedings) Publisher：IOP PUBLISHING LTD

We have carried out the electrical resistivity measurements under high pressures up to 24 GPa for CeTX3 (T: Co and Ir, X: Si and Ge), CePd5Al2 and YbIr2Zn20 in order to investigate quantum criticality and superconductivity. Antiferromagnets CeTX3 with the non-centrosymmetric tetragonal structure show superconductivity under high pressures and reveal a huge upper critical field for H parallel to [001]. An antiferromagnet CePd5Al2, which is an isostructural family of a heavy fermion superconductor NpPd5Al2, also shows superconductivity under high pressures. In these compounds, superconductivity appears in the vicinity of quantum critical point. On the other hand, YbIr2Zn20 without magnetic ordering approaches to the quantum critical point with increasing pressure, and exhibits a super-heavy fermion state exceeding 10 J/(K-2 center dot mol).

DOI： 10.1088/1742-6596/400/2/022028

Electronic states and superconducting properties of non-centrosymmetric rare earth compounds Reviewed

Yoshichika Onuki, Rikio Settai

Lecture Notes in Physics 847 81 - 126 2012

Language：English Publishing type：Research paper (scientific journal)

The property of Fermi surface splitting in the non-centrosymmetric tetragonal compounds RPt 3Si (R: La, Ce) and RT X 3 (T: Co, Rh, Ir
X: Si, Ge) are studied by de Haas-van Alphen experiments and compared with energy band calculations. Moreover superconducting properties are investigated in these compounds. In particular, in CeIrSi 3 the unusual behavior of the upper critical field H c2 at pressures around 2.6 GPa is analyzed in detail. At 2.6 GPa, a huge value of H c2(0) ≃450 kOe is found for magnetic fields along the [0 0 1] direction of the non-centrosymmetric tetragonal crystal structure, in contrast to the smaller H c2(0) ≃ 95 kOe for H ∥ [1 1 0]. © Springer-Verlag Berlin Heidelberg 2012.

DOI： 10.1007/978-3-642-24624-1_3

Systematic study of the 4f electronic state in RRhIn <inf>5</inf> and RCu <inf>2</inf>Si <inf>2</inf> (R: Rare earth)

Tetsuya Takeuchi, Tetsuya Takeuchi, Nguyen Van Hieu, Nguyen Duc Dung, Yuji Takeda, Yasunori Nakano, Kiyohiro Sugiyama, Rikio Settai, Yoshichika Onuki, Tatsuma D. Matsuda, Etsuji Yamamoto, Yoshinori Haga

e-Journal of Surface Science and Nanotechnology 9 446 - 453 2011.12

Language：English Publisher：The Surface Science Society of Japan

Systematic study of the 4f electronic state in RRhIn 5 and RCu 2Si 2 has been done by using single crystalline samples which were successfully grown by the flux method. Most of RRhIn5 compounds order antiferromagnetically at low temperatures, except when R=Y, La, Pr and Yb. The observed anisotropic features in the magnetic susceptibility and magnetization have been analyzed on the basis of the crystalline electric field (CEF) model. The observed anisotropy in the magnetic susceptibility in the paramagnetic state is well explained by the CEF effect. Specific heat measurements on a series of ternary compound RCu 2Si 2 have been performed by the quasiadiabatic heat pulse method in the temperature range down to 100 mK. We observed the nuclear specific heat at low temperatures and estimated the magnitude of internal effective magnetic field H eff at the nucleus in RCu 2Si 2. © 2011 The Surface Science Society of Japan.

DOI： 10.1380/ejssnt.2011.446

Pressure and Temperature Dependences of the Electronic Structure of CeIrSi3 Probed by Resonant X-ray Emission Spectroscopy Reviewed

Hitoshi Yamaoka, Ignace Jarrige, Naohito Tsujii, Akio Kotani, Jung-Fu Lin, Fuminori Honda, Rikio Settai, Yoshichika Onuki, Nozumu Hiraoka, Hirofumi Ishii, Ku-Ding Tsuei

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 ( 12 ) 2011.12

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

Pressure and temperature dependences of the electronic structure of the heavy-fermion superconductor CeIrSi3 have been investigated using partial fluorescence yield x-ray absorption spectroscopy and resonant x-ray emission spectroscopy at the Ce L-3 edge. Ce is in a weakly mixed valence state at ambient pressure, mostly f(1) with a small contribution from the f(0) component. Pressure-induced increase of the Ce valence becomes apparent above 4 GPa, concomitantly with the disappearance of the superconductivity. No temperature dependence of the Ce valence is observed within the measured temperature range down to 24 K.

DOI： 10.1143/JPSJ.80.124701

Electronic structure of YbCu2Ge2 studied by soft x-ray angle-resolved photoemission spectroscopy Reviewed

A. Yasui, S. -I. Fujimori, I. Kawasaki, T. Okane, Y. Takeda, Y. Saitoh, H. Yamagami, A. Sekiyama, R. Settai, T. D. Matsuda, Y. Haga, Y. Onuki

PHYSICAL REVIEW B 84 ( 19 ) 2011.11

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER PHYSICAL SOC

We have measured three-dimensional band structure and Fermi surfaces (FSs) ofYbCu(2)Ge(2), which has recently become recognized as a nearly divalent Yb-based compound, by using soft x-ray angle-resolved photoemission spectroscopy. We clarified that the bands with finite Yb 4f contribution cross the Fermi level and are slightly involved in the formation of the FSs, in line with the valence-fluctuating state of YbCu2Ge2. The obtained valence-band dispersions and the FSs are well explained by a relativistic band-structure calculation based on a local-density-approximation (LDA). These results suggest that the LDA calculation is a good starting point for understanding of the electronic state of YbCu2Ge2 as well as nearly divalent Yb-based compounds.

DOI： 10.1103/PhysRevB.84.195121

Field-Induced Quadrupolar Ordered Phase for H parallel to < 111 > in Heavy-Fermion Compound YbCo2Zn20 Reviewed

Tetsuya Takeuchi, Shingo Yoshiuchi, Masahiro Ohya, Yuki Taga, Yusuke Hirose, Kiyohiro Sugiyama, Fuminori Honda, Masayuki Hagiwara, Koichi Kindo, Rikio Settai, Yoshichika Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 ( 11 ) 2011.11

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

Magnetic susceptibility, high-field magnetization up to 500 kOe, and specific heat in a wide temperature range from 0.06 to 300K were measured for single crystals of the cubic heavy-fermion compound YbCo2Zn20 in order to elucidate the electronic states of the compound at low temperatures. A strong increase in the magnetic specific heat in the form of C-mag/T below similar to 1K is approximately explained by the resonant level model for S = 1/2 with the Kondo temperature T-K = 1 K, and an extremely large C-mag/T similar or equal to 8 J/(K-2.mol) below about 0.2K is explained by considering the magnetic entropy of the doublet ground state in the 4f crystalline electric field (CEF) scheme of an Yb3+ ion, which corresponds to an extremely large electronic specific heat coefficient. The field-induced ordered phase for H parallel to < 111 >, which has recently been found by low-temperature magnetization measurements, was precisely studied by electrical resistivity and specific heat measurements, and was observed in a limited angular range around the < 111 > direction. On the basis of CEF analyses, the level crossing of the two lowest CEF states is essentially important to understand the field-induced ordered phase, which can be reduced to a field-induced antiferro-quadrupolar ordering based on the Gamma(3)-type quadrupole moment O-2(0).

DOI： 10.1143/JPSJ.80.114703

Field-Induced Antiferromagnetic State in Non-centrosymmetric Superconductor CeIrSi3 Reviewed

Rikio Settai, Keisuke Katayama, Dai Aoki, Ilya Sheikin, Georg Knebel, Jacques Flouquet, Yoshichika Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 ( 9 ) 2011.9

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We have carried out the electrical resistivity and ac specific heat measurements under pressure P and magnetic field H in a pressure-induced superconductor CeIrSi3 with the noncentrosymmetric tetragonal crystal structure. Superconductivity is observed in a wide pressure region from 1.9 GPa to about 3.5 GPa. The antiferromagnetic state disappears at P-c = 2.25 GPa under H = 0, but in magnetic field we have found an antiferromagnetic state. The corresponding electrical resistivity in constant magnetic field decreases rather steeply below the Neel temperature T-N under pressures up to about 2.4 GPa, while it shows an upturn anomaly at T-N under pressures larger than 2.4 GPa. The ac specific heat also indicates a clear jump at T-N in magnetic field. When the antiferromagnetic phase exists in magnetic field, the superconducting transition becomes broad, possessing a transition width Delta T-sc = 0.2-0.5 K. On the other hand, it becomes extremely sharp, with Delta T-sc = 0.03K even at 17 T under P = 2.55 GPa, for example, when the antiferromagnetic phase disappears. The upper critical field H-c2 for H parallel to [001] is also extremely enhanced around 2.5-2.7 GPa, and the H-c2(0) value reaches about 45 T at P-c* similar or equal to 2.63 GPa, even though the superconducting transition temperature T-sc = 1.6K is very small. The electronic instability is realized in magnetic field at P-c*. The present characteristic heavy fermion superconductivity in the noncentrosymmetric structure is compared with the similar pressure-induced superconductivity of CeRhIn5.

DOI： 10.1143/JPSJ.80.094703

High Field Magnetoresistance and de Haas-van Alphen Effect in LaRu2Al10 Reviewed

Masahito Sakoda, Shuhei Tanaka, Eiichi Matsuoka, Hitoshi Sugawara, Hisatomo Harima, Fuminori Honda, Rikio Settai, Yoshichika Onuki, Tatsuma D. Matsuda, Yoshinori Haga

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 ( 8 ) 2011.8

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We have measured the magnetoresistance and de Haas-van Alphen (dHvA) effect in LaRu2Al10, which is a reference compound of CeRu2Al10 that exhibits an unusual transition at T-0 similar or equal to 27 K. The magnetoresistance increases with increasing magnetic field at low temperatures in the wide field directions, suggesting that LaRu2Al10 is a compensated metal without an open orbit. From the dHvA experiments, about three dHvA frequency branches whose cyclotron effective masses are close to 1m(0) (m(0): rest mass of an electron) were detected. The observed dHvA branches for the main Fermi surface are well explained by the results of band structure calculation based on a full potential linearized augmented-plane-wave (FLAPW) method and local-density approximation (LDA), that demonstrates the multiply connected Fermi surface with no nesting property in LaRu2Al10.

DOI： 10.1143/JPSJ.80.084716

Pressure-induced structural phase transitions in UIr Reviewed

H. Kotegawa, S. Araki, T. Akazawa, A. Hori, Y. Irie, S. Fukushima, H. Hidaka, T. C. Kobayashi, K. Takeda, Y. Ohishi, K. Murata, E. Yamamoto, S. Ikeda, Y. Haga, R. Settai, Y. Onuki

PHYSICAL REVIEW B 84 ( 5 ) 2011.8

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER PHYSICAL SOC

Strain and resistivity measurements in UIr showed the occurrence of two structural phase transitions under high pressure, indicating the existence of three phases I-III, with slightly different crystal structures. It is suggested that ferromagnetic phases FM1-FM3 emerge in phases I-III, respectively. The pressure-temperature phase diagram was sensitive to the hydrostaticity of pressure. FM3 and superconductivity are observed in the measurements in which Daphne 7373 is used as a pressure-transmitting medium; however they are both absent in the case where petroleum ether is used as a pressure-transmitting medium. These results indicate a close relationship between ferromagnetism and superconductivity.

DOI： 10.1103/PhysRevB.84.054524

Characteristic Heavy Fermion Properties in YbCu2Si2 and YbT2Zn20 (T: Co, Rh, Ir) Reviewed

Yoshichika Onuki, Shinichi Yasui, Masaki Matsushita, Shingo Yoshiuchi, Masahiro Ohya, Yusuke Hirose, Nguyen D. Dung, Fuminori Honda, Tetsuya Takeuchi, Rikio Settai, Kiyohiro Sugiyama, Etsuji Yamamoto, Tatsuma D. Matsuda, Yoshinori Haga, Toshiki Tanaka, Yasunori Kubo, Hisatomo Harima

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 2011.7

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We studied the Fermi surface properties of YbCu2Si2 and YbCu2Ge2 with the tetragonal structure by measuring the de Haas-van Alphen (dHvA) oscillations, together with the energy band calculations. It was clarified that 4f electrons contribute to the Fermi surface of a valence fluctuating compound YbCu2Si2, but not to that of a divalent compound YbCu2Ge2. Namely, the Fermi surface of YbCu2Si2 contains the 4f-components considerably and the corresponding cyclotron effective mass m(c)* of the main Fermi surface is large, m(c)*=30-40m(0) (m(0) : rest mass of an electron). We also studied the heavy fermion properties of YbT2Zn20 (T : Co, Rh, Ir) with the cubic caged structure. The metamagnetic behavior or an abrupt nonlinear increase of magnetization was observed at 6 kOe in YbCo2Zn20, 63 kOe in YbRh2Zn20, and 97 kOe in YbIr2Zn20 for H parallel to < 100 >, which was measured at 60 mK in YbCo2Zn20 and 1.3 K in YbRh2Zn20 and YbIr2Zn20. The metamagnetic field is found to be a good parameter to reach the quantum critical point under pressure for YbIr2Zn20. By measuring the electrical resistivity under pressure and magnetic field, we clarified that the electronic state close to the quantum critical point is realized in YbIr2Zn20 at 5.2 GPa and also YbCo2Zn20 at ambient pressure. The corresponding heavy cyclotron effective mass of 100-500m(0) at 0 kOe was estimated from the field dependence of the root A value in the low-temperature electrical resistivity rho = rho(0) + AT(2) under pressure and magnetic field and the cyclotron mass obtained from the dHvA experiment at ambient pressure and high magnetic fields.

DOI： 10.1143/JPSJS.80SA.SA003

High-Field de Haas-van Alphen Effect in non-centrosymmetric CeCoGe3 and LaCoGe3 Reviewed

Ilya Sheikin, Pierre Rodiere, Rikio Settai, Yoshichika Onuki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 2011.7

Language：English Publishing type：Research paper (scientific journal) Publisher：PHYSICAL SOC JAPAN

We report on de Haas-van Alphen effect measurements in the non-centrosymmetric systems CeCoGe3 and LaCoGe3 in magnetic field up to 28 Testa. In both compounds, two new high frequencies were observed in high fields. The frequencies were not detected in previous lower field measurements. The frequencies do not originate from magnetic breakdown, and, therefore, are likely to be intrinsic features of the compounds. In CeCoGe3, the corresponding effective masses are strongly enhanced, being of the order of 30 bare electron masses.

DOI： 10.1143/JPSJS.80SA.SA020

　 PREV - NEXT 　

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22